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AbstractAbstract
[en] In single-chamber solid oxide fuel cells (SC-SOFC), anode and cathode are placed in a gas chamber where they are both exposed to a fuel/air mixture. Similarly to conventional dual-chamber SOFC, the anode and the cathode are separated by an electrolyte, but in the SC-SOFC configuration it does not play tightness role between compartments. For this reason, the electrolyte can be processed by screen printing, a technique particularly appropriated for preparing thick porous layers. However, it is necessary to have a diffusion barrier to prevent the transportation of hydrogen produced locally at the anode to the cathode through the electrolyte that reduces fuel cell performances. This study aims to obtain directly a diffusion barrier through the surface densification of the electrolyte by a laser treatment which allows to induce modifications on materials with localized thermal annealing minimizing heating of the underlying substrate. The material chosen for the electrolyte was cerium gadolinium oxide Ce0.9Gd0.1O1.95 (CGO) which is deposited by screen printing on a composite NiO-CGO anode. UV laser and IR laser irradiations were used at different fluences and number of pulses to modify the density of the electrolyte coating. Microstructural characterizations confirmed the modifications on the surface of the electrolyte for appropriate experimental conditions showing either grain growth or densified but cracked surfaces. Structural and chemical modifications on the surface were evaluated as well as the gas diffusion through the electrolytes and their electrical conductivity. In order to understand interaction between the laser and the material, thermal modelling was also developed. Finally, SC-SOFC performances were improved for the cells presenting grain growth at the electrolyte surface, particularly, the power density has been enhanced by a factor 2 (21 mW cm-2 compared to the reference without laser treatment 11 mW cm-2). (author)
[fr]
Dans les piles a combustible SOFC (Solid Oxide Fuel cell) de type monochambre (SC-SOFCS), l'anode et la cathode, separees par un electrolyte, sont situees dans une meme chambre alimentee par un melange de combustible et d'oxygene. L'electrolyte, n'ayant alors plus le role d'etancheite entre les compartiments anodique et cathodique, peut etre mis en forme par serigraphie, technique particulierement adaptee pour preparer des revetements poreux. Malgre tout, dans ces systemes monochambre, il est necessaire d'avoir une barriere pour eviter la possible diffusion de l'hydrogene produit localement a l'anode vers la cathode, ce qui peut generer une chute de la tension. L'objectif de ce travail de these est de creer une barriere de diffusion localisee via la densification de la surface de l'electrolyte par un traitement laser, ce qui permet de ne pas densifier les autres couches comme pourrait le faire un traitement thermique conventionnel. Le materiau selectionne pour l'electrolyte est un oxyde mixte de cerium gadolinium Ce0,9Gd0,1O1,95 (CGO) qui est depose par serigraphie sur une anode composite NiO-CGO. Deux types de lasers impulsionnels sont utilises dans cette etude: un laser UV excimere KrF (λ = 248 nm) et un laser IR a fibre dopee a l'ytterbium (λ = 1064 nm). Les caracterisations microstructurales realisees ont permis de mettre en evidence les effets du traitement laser pour certaines combinaisons fluence - nombre de tirs, montrant un grossissement de grain de l'electrolyte ou bien des surfaces densifiees mais fissurees. Des modifications structurales et chimiques sur la surface ont ete evaluees ainsi que la diffusion de gaz au travers des electrolytes modifies tout comme leur conductivite electrique. Afin de mieux comprendre l'interaction laser-matiere, une modelisation thermique a egalement ete mise en oeuvre. Finalement, les performances de piles SC-SOFC ont ete ameliorees pour les dispositifs presentant un grossissement de grain a la surface de l'electrolyte ou, en particulier, un doublement de la densite de puissance (21 mW.cm-2) par rapport a la reference sans traitement laser (11 mW.cm-2). (auteur)Original Title
Modification de la porosite de Ce0,9Gd0,1O1,95 par traitement laser: application pile SOFC monochambre
Primary Subject
Source
19 Dec 2016; 169 p; 107 refs.; Available from the INIS Liaison Officer for France, see the INIS website for current contact and E-mail addresses; These de Doctorat de l'Universite de Lyon, Specialite: Genie des Procedes
Record Type
Miscellaneous
Literature Type
Thesis/Dissertation
Report Number
Country of publication
CERIUM COMPOUNDS, CHALCOGENIDES, COHERENT SCATTERING, DIFFRACTION, DIRECT ENERGY CONVERTERS, ELECTRICAL PROPERTIES, ELECTROCHEMICAL CELLS, ELECTRON SPECTROSCOPY, FUEL CELLS, GADOLINIUM COMPOUNDS, HEAT TREATMENTS, HIGH-TEMPERATURE FUEL CELLS, MACHINING, OXIDES, OXYGEN COMPOUNDS, PHOTOELECTRON SPECTROSCOPY, PHYSICAL PROPERTIES, RARE EARTH COMPOUNDS, SCATTERING, SIMULATION, SOLID ELECTROLYTE FUEL CELLS, SPECTROSCOPY
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